Composition for the detection of moisture in polar organic liquids



United States Patent 3,222,292 COMPOSITION FOR THE DETECTION OF MOIS- TURF. IN POLAR ORGANIC LIQUIDS Francis Joseph Nadolski, Piscataway Township, Middlesex County, N J assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed June 8, 1962, Ser. No. 200,954 9 Claims. (Cl. 252-408) This invention relates to a method for detecting moisture in polar organic liquids which are at least partially miscible with Water; to dye compositions useful therein; and to the polar organic liquids containing such dye compositions.

Many organic liquids in the ordinary course of manufacture, use, or storage, tend to become contaminated with moisture. For some uses it is necessary to employ the organic liquid in a substantially anhydrous state. The problem of removing water as a contaminant is not as difficult to solve as the problem of detecting its presence. This difficulty is attenuated in the case of hydroscopic polar liquids, since, of course, these pick up moisture when stored in a container which is open or even imperfectly closed.

A good example of the everyday occurrence of this problem is the case of brake fluids. In ordinary use, the brake fluid picks up moisture from the air. An open brake fluid can, the transfer from can to brake system, and further, each use of the brake with exchange of air through the vent holes in the master cylinder, adds moisture to the brake fluid. As the number and frequency of stops increases or in emergency braking at high speed, the temperature of the brake fluid increases. Many other factors contribute to the raising of the temperature of the brake fluid. As the brake fluid becomes hot enough to boil, vapor bubbles are formed in the cylinders. Vapor, as opposed to liquid, is very compressible and braking action is lost since applied pressure simply compresses the vapor and does not energize the brakes. This is known as vapor lock. The presence of water also lowers the boiling point of the brake fluid. Laboratory tests show that when as little as 2% Water is present in the brake systern, the boiling point of the heavy duty brake fluid falls below the legal specification. The practical limit of water content for safe driving is 3%. When the water content exceeds this, the brake fiuid should be changed and new anhydrous brake fluid added from a sealed can.

For the purpose of this description a polar liquid is one which consists of molecules Which are electrically polarized and thus are held together by electrical forces. The number of such liquids in common usage is extremely large, as is the number of applications in which these liquids are required to be in substantially anhydrous condition. There are many ways by which small amounts of moisture contamination can be either qualitatively or quantitatively determined, but they are for the most part quite involved and require a good amount of skill for use. These methods for moisture detection generally include absorption of water on a chemical drying agent, or extraction, distillation, centrifuging and measurement of the weight obtained. The weight of Water can be converted to a percent moisture contamination value. The prior art method of choice is ASTM Dl364-58. It is the official test for moisture ofthe American Society of Testing Materials and employs the Carl-Fischer titrimetric method using an iodine end point. It requires apparatus, iodine, sulfur dioxide, pyridine and methanol, and of course is too cumbersome ever to be used by an unskilled person. These and other heretofore available methods, of course, are useful when trained technical personnel and the proper equipment are both available. Absent these requisites, as in manyon-the-spot applications, there was until the present time no feasible Way for simply detecting moisture contamination.

In view of this state of the art, it is an object of the present invention to provide a method for detecting moisture even when present in low concentration in polar organic liquids which are at least partially Water miscible.

It is a further object of this invention to provide dye compositions which can be added to such polar organic liquids and which will, by a visible color change, indicate the presence of moisture above a given concentration.

It is still another object of the present invention to provide a polar organic liquid containing such a dye composition, which mixture upon the absorption of a small amount of water, visibly changes its color.

Other objects will be obvious to one skilled in the art from the following description of the invention.

In accordance with this invention it has been discovered that when l-hydroxy 4 acetamino-anthraquinone, represented by the following formula:

is incorporated in the polar organic liquid along with a small amount of an amine or an inorganic base having an ionization greater than about 3 10 an orange colored mixture is obtained, if the mixture is substantially anhydrous. But in the presence of even a small amount of moisture, i.e., about one and one-half per cent, the color of this body of liquid becomes blue-red, and the difference is easily discernable to even an untrained eye.

It is indeed surprising that this anthraquinone dyestuff is capable of giving a color change under these conditions, since many closely related dyestuffs, as will be hereinafter described, are inoperative in this capacity. Thus the structurally related compound 1-hydroxy-4-anilinoanthraquinone, while coloring the solution in theabsence of moisture, does not change its color in the presence of Water.

The practice of this invention is extremely simple, involving only the admixture of the dyestuif, the organic amine or inorganic base and the polar organic liquid in any sequence. The dye may be added to the polar liquid, followed by the organic amine or vice versa, or else a mixture of the dye stuff and the amine may be prepared beforehand and used as necessary either by addition to the whole body of the liquid or to a test sample thereof.

It is an important advantage of the present invention that only minor amounts of dyestuif in proportion to the organic liquid, will give an observable color change. Dye concentrations as low as about 0.0005% by weight, will give discernible color changes. On the other hand, much more, up to 1% and even higher, may be employed. Visibility of the color change upon the advent of a moisture content of about 1 or 1.5%, depends on several factors. When a high concentrtaion of the dyestuff is employed, the body of liquid tends to become opaque, making color evaluation diflicult, unless only a thin section of the liquid is observed. Thus, a sample may be placed on a glass slide or porcelain plate for viewing. Use of low concentrations of dyestuff (i.e., in the lower regions of the aforementioned range) of course results in the dilution of the color change, making the color change more diflicult to discern. For these reasons, for practical purposes the concentration of the dyestuif, on a weight basis, should be within the range of 0.001% to 0.0125%, with around 0.005% to 0.01% being preferred.

So long as an organic amine or inorganic base has an ionization constant greater than 3 10-=, it is useful in the present invention regardless of its chemical structure. For many purposes, however, other qualifications may be desirable. Thus, if the moisture detector composition of this invention is to be incorporated in a liquid to be used in an open system and/or at ambient temperatures or above, it is generally desirable that it should not be volatile. Likewise if the organic liquid is to be subjected to extreme temperatures, the amine or inorganic base should be one which is soluble under those conditions. These factors, of course, are entirely dependent upon the intended use of the organic liquid. The list of suitable amines is extremely large. Included therein are such amines as: Ethanolamine, diethanolamine, triethanolamine, ethanolpropanolamine, dipropanolamine, 2-dimethylaminothanol, Z-diethylaminoethanol, 3-methyloxy propylamine, 3-dimethylaminopropylamine, 3,3'-iminobispropylamine, diisoamylamine, dibutylamine, dipropylamine, isopropanolamine, benzylamine, beta phenethylamine, tripropylamine, tri-isobutylamine, ethylenediamine, propylenediamine, tetraethylenediamine, piperidine, alphaalanine, butylamine, conniine, diisoamylamine, diethylamine, diethylbenzylamine, p-methoxybenzylamine, N,N- methoxybenzylamine, N,N-methylbenzylamine, methyldiethylamine, 4-phenylbutylamine and spartiine.

The concentration of the organic amine or inorganic base is not critical. It should be suflicient to catalyze hydrolysis of a sufficient quantity of the dyestuif to produce a visible color change when moisture reaches the abovenamed level. It is difficult to give a numerical value to this minimum quantity since it varies with the ionization constant of the substance, the concentration of the dye, the polarity of the liquid, or the presence of small amounts of components or contaminants which must first be neutralized. There is virtually no upper limit to the concentration since polar fluids which are organic amines can be tested for moisture content by incorporating the proper amount of the dyestuff therein. In other words, the upper limit depends upon the amount which can be tolerated in the organic liquid for the intended purpose. When the organic liquid is not a base having an ionization constant greater than 3 l0 there may however be a practical limit to the concentration of the amine. This limit may be roughtly stated as being about 1000% by weight of the dyestuff. The lower limit of amine or base concentrations in preferred practice is approximately equal to the equivalents necessary to hydrolyze the acetyl group from the anthraquinone dyestuff.

Operable in the compositions of this invention, in place of the organic amine, are strong inorganic bases such as alkali hydroxides and salts of strong bases with weak acids. An example of the latter is borax, which in the presence of water, hydrolyzes to form sodium hydroxide and tetraboric acid. Strong inorganic bases can damage rubber, especially acrylate rubber often used in certain parts of a brake system. Organic amines are preferred for heavy duty brake fluids. However inorganic bases are cheaper and can be used in certain compositions for containers or systems not vulnerable to attack.

It is an advantage of this invention that it is applicable to any polar organic liquid which is either neutral or basic and is capable of dissolving at least about 1.0% (by weight) water. Acidic liquids tend to react with the free amine thus preventing it from catalyzing the hydrolysis of the anthraquinone dyestuif. Therefore, such acids as thiophenol, oleic acid and phenol would not be operable. Likewise, since a minimum amount of water is required for the hydrolysis of the anthraquinone dyestuif to its redblue form, liquids not having the capacity to dissolve this amount cannot be tested in accordance with this invention. As stated above, this minimum amount is a water concentration equal to about 1.5% by weight of the polar liquid. Therefore, on this ground, substances such as dioctylphthalate which dissolve only 0.2% on their weight of water are excluded. The class of useful polar organic fluids is varied and far-reaching, since it includes all liquids which are even slightly water-miscible and non-acidic.

Among those which may be named for purposes of illustration are the following:

(a) Alcohols (either monohydric or polyhydric) e.g.,

methanol, ethanol, propanol, isopropanol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, 3-pentanol, n-hexyl alcohol, methylamyl alcohol, 2-ethylbutyl alcohol, cyclohexanol, 3 heptanol, ethylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, glycerol, furfuryl alcohol;

(b) Ethers such as dioxane;

(c) Ether-alcohols such as Z-methoxyethanol, 2-ethoxyethanol, l-methoxy-Z-propanol, 1-ethoxy-2-propanol, 2- (2 methoxyethoxy)ethanol, 2 (2 ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)-ethanol, monomethyl ether of dipropylene glycol and 2-phenoxyethanol;

(d) Ketones such as acetone, diacetone alcohol, acetoxyacetone and methyl ethyl ketone;

(e) esters such as ethylene carbonate, ethyl lactate, -2-

methoxyethyl lactate, methoxy triglycol acetate, methyl formate, methyl acetate, propylene carbonate, tributylphosphate and ethyl formate;

(f) amines such as pyridine and those liquid amines having an ionization constant less than 3 -10* The present invention also contemplates moisture detection in mixtures of two or more organic liquids. In this event only one of the component organic liquids need be partially water-miscible. Such mixtures are found in various commercially important compositions including industrial solvents, heat transfer liquids and hydraulic brake fluids and will be exemplified in the following examples which are presented to further illustrate the present invention. Parts are by weight unless otherwise stated.

EXAMPLE 1 Color change in brake fluid with moisture An anhydrous brake fluid A is prepared as follows. The following parts by volume are mixed:

200 parts of polypropylene glycol 1200 600 parts of the monomethyl ether of diethylene glycol parts of diethylene glycol 110 parts of propylene glycol To the mixture is added 7.5 parts of isopropylene-bis- (4,4-phenol) and 15 parts of dibutylamine. The resultant anhydrous brake fluid A is divided in half. To half is added 1 part of 4-acetylamino-l-hydroxyanthraquinone to give a stock orange indicator dye solution of the anthraquinone dye in anhydrous brake fluid which will be called B. Four parts by volume of the orange indicator dye solution of B is added to successive portions of parts by volume of anhydrous brake fluid A. A redorange solution of the indicator dye in the anhydrous brake fluid is obtained. Water is then added to each portion in the amount shown in the left-hand column of Table I below. The portion is then shaken and the color observed. This color is given in the right-hand column of Table I.

TABLE I Observed Color in Brake Fluid Contaming Indicator Dye Percent Cone. Water 0 Red-orange.

1.5 Blue-red.

2.0 Distinct; blue-red.

EXAMPLE 2 Preferred concentration of dye and limits If to successive equal portions of the anhydrous brake fluid A employed in Example 1, is added suflicient 4- 5 acetylamino lhydroxy anthraquinorie indicator dye to give a concentration indicated in the left-hand column, the color observed in anhydrous and moist brake fluid is as follows:

TABLE II Color of Brake Fluid Dye Cone.

Anhydrous 2% Water Added Light orange Light blue-red. Orange Blue-red. Strong orange Strong blue-red. Very strong orange. Very strong blue-red.

For direct viewing in a test tube of a l-ml. sample, the best dye strength is 0.008%. It a 0.05% solution is used for evaluation, it should be dropped on a watch glass or glass plate to give a center section for viewing. Also it may be dropped on a white porcelain plate, or a capillary tube or a rod may also be used. The color change is striking and readily verified.

EXAMPLE 3 To lO-ml. by volume of each of the polar organic liquids listed in the left-hand column (used in brake fluid formulations), is added the indicator dye used in Example 2 in an amount to give 0.008% concentration. The dye dissolves readily in all liquids listed to give equivalent redorange solutions. On addition of 2% of water to each sample, no change of color takes place. However, when one drop of ethylene diamine is added to each sample containing the 2% water, a change to blue-red color occurs.

TABLE III Organic Fluid Containing 2% Water-{- 0.008% Dyestufi 2% Water Ethylenediamine Ethylene glycol Red-orange- Blue-red Carbitoldo Do. Cellosolve Do. Methyl Cellosolve Do. Aceton Do. Ethyl alcohol Do. n-Butyl alcohol Do. Castor oil. Do. Heavy duty brake fluid (mixture of Do.

Example 1 minus the bisphenol and dibutylamine).

The above results show that the color change takes place in the presence of an organic base. Also it shows that the indicator dye of this invention can be used for moisture detection in diverse polar organic solvents miscible with water.

EXAMPLE 4 To 10-ml. each of successive samples of propylene glycol containing 0.008% indicator dye and 2% water is added a drop of the following amines. The strength of the amine is given in the middle column and the color observed on mixing is given in the right-hand column.

TABLE IV Ionization Amine Constant Color Observed (K Value) Pyridine. 1. 4X10 Orange color-no change. Ethanolamme 2. 77 X10- Blue-red. Ethylenediarm'ne 8. 5X10 Do. Tetramethylene diamine 4.1 Do. Dlethylamine 1. 26 10- Do.

A similar change takes place if a pellet of sodium hydroxide is added instead of an organic base. The color becomes a strong blue-red.

Most aromatic amines like pyridine and aniline are too weak to be operable as the organic base. Hydrazine does not give a distinct change. The amine employed by this 6 invention should therefore be stronger than hydrazine. Hence it should have an ionization constant greater than 3 X 10-.

EXAMPLE 5 The following dyes cannot be used to detect moisture by the method herein disclosed. They do not show the requisite color change at the critical range of moisture content.

EXAMPLE 6 The following mixture is prepared:

50 parts castor oil 35 parts monoethylether of ethylene glycol 5 parts N-ethyl o-toluenesulfonamide 5 parts N-ethyl p-toluenesulfonamide 5 parts N-methyl p-toluenesulfonamide 0.02 part of 4-acetylamino-d-hydroxyanthraquinone To this mixture is added tripropylamine sulficient to neutralize free ricinoleic acid present in the castor oil. A further amount of tripropylamine, 1.0 part, is then added. The resultant orange fluid is useful as a brake fluid. Upon the addition of 2% water the color change is blue red.

In place of tripropylamine, an equal amount of di-isoamyalmine, tri-isobutylamine or trimethylene diamine may be used with the same results.

EXAMPLE 7 The .following mixture is prepared:

70 parts funfuryl aldehyde 29 parts furfuryl alcohol 0.01 part 4acetylamino-l-hydroxyanthraquinone 1 part tri-isobutyl-amine This orange composition is useful as a brake fluid and in other systems for hydraulic transmission of power. Upon the addition of 1.5% water a change in color from orange to blue-red is noted.

EXAMPLE 8 One drop of a mixture containing 5 parts of tripropyl amine per part of 4acetylamino-l-hydroxyanthraquinone is added to anhydrous glycerol. The glycerol becomes orange colored. Upon the addition of water to a weight concentration of 1.5% a color change from orange to blue-red is noted.

Substitution of triethanolamine, propylenediamine or pmethoxybenzylamine in the foregoing procedure produces similar results.

I claim:

- '1. A method for detecting the presence of water in a non-acidic, polar organic liquid miscible with water to the extent of at least about 15% thereof which comprises (-1) adding to said liquid (a) the dye, 4-acetylamino-lhydroxyanthraquinone, and (b) an organic amine having an ionization constant greater than 3X10 the amount of (a) added being suficient to provide a concentration of from about 0.0005% to about 1% by weight thereof in said liquid and the amount of (b) added being sufficient to effect a visible color change in said liquid when said liquid has a water content above about 1.5% and (2) visually observing any color change in said liquid.

2. The method of claim 1 wherein the amount of dye (a) added is from about 0.005% to about 0.01%.

3. A composition consisting essentially of (a) a nonacidic, polar organic liquid miscible with water to the extent of at least about 1.5% by weight thereof, (b) from about 0.0005 to about 1%, by weight, of the dye, 4-acetylarnino-1-hydroxyanthraquinone, and (c) an organic amine having an ionization constant greater than 3 10- in an amount suflicient to effect a visible color change in said liquid when said liquid has a water content above about 1.5%.

4. The composition of claim 3 wherein the polar liquid consists essentially of an ethylene glycol.

5. The composition of claim 3 wherein the polar liquid consists essentially of castor oil and monoethyl ether of ethylene glycol.

6. The composition of claim 3 wherein the amine is dibutylamine.

7. The composition of claim 3 wherein the amine is ethylene diamine.

8. The composition of claim 3 wherein the amine is ethanolamine.

9. The composition of claim 3 wherein the amine is tripropylamine.

References Cited by the Examiner UNITED STATES PATENTS 2,155,673 4/1939 Miller 260-377 2,819,274 1/1958 Grossmann 260-377 2,968,940 1/1961 =Feldman et a1 252408 3,003,353 IO/ 1961 Swadesh 73-53 3,041,870 7/1962 Levine 7353 JULIUS GREENWALD, Primary Examiner. 

3. A COMPOSITION CONSISTING ESSENTIALLY OF (A) A NONACIDIC, POLAR ORGANIC LIQUID MISCIBLE WITH WATER TO THE EXTENT OF AT LEAST ABOUT 1.5% BY WEIGHT, THEREOF, (B) FROM ABOUT 0.0005% TO ABOUT 1%, BY WEIGHT, OF THE DYE, 4-ACETYLAMINO-1-HYDROXYANTHRAQUINONE, AND (C) AN ORGANIC AMINE HAVING AN IONIZATION CONSTANT GREATER THAN 3X10-**6 IN AN AMOUNT SUFFICIENT TO EFFECT A VISIBLE COLOR CHANGE IN SAID LIQUID WHEN SAID LIQUID HAS A WATER CONTENT ABOVE ABOUT 1.5%. 